This invention relates generally to apparatus for reinforcing vertical columns such as supports in bridges and over passes, and more particularly the invention relates to apparatus for applying a reinforcing coil of wire around a column.
Concrete columns typically can support large compressive forces but are less resistant to torsion and bending forces which can be imparted thereto during an earthquake, for example. Cracks in the columns resulting from an earthquake can allow concrete particles to dislodge from the column.
Prior to the 1971 San Fernando earthquake in California spiral reinforcing of the vertical steel bars in reinforced concrete columns was not required or used. During the 1971 earthquake many columns failed due to the vertical bars breaking loose from the concrete columns, especially around joints.
Since 1971 spiral reinforcing has been required for the vertical bars prior to the pouring of concrete.
The present invention is directed to apparatus for reinforcing columns, especially pre-1971 columns, to provide containment of the vertical steel bars and prevent loss of concrete.